Polyvinyl chloride fibers

ABSTRACT

Vinyl chloride homo- and co-polymers are made which have uniform cross section, homogeneous structure, great brilliance, and good transparency. They are far superior in these properties to any polyvinyl chloride homo- or co-polymers which were previously known. They may have any desired shape in cross section, for instance those of a square or a star.

United States Patent Ledoux et al.

March 3, 1967 France....

[ June 27, 1972 POLYVINYL CHLORIDE FIBERS Inventors: Claude Ledous,Antony, Hauts de Seine;

Albert De Vries, Chevilly-Larue, Val de Marne, both of France ProduitsChimiques Pechlney Saint Gobain, Neuilly sur Seine, France Filed: Oct.30, 1969 Appl. No.: 872,560

Related US. Application Data Continuation-impart of Ser. No. 638,177,April 24, 1967, Pat. No. 3,548,049.

Assignee:

Foreign Application Priority Data April 27, 1966 France"... ..6659303Oct. 9, 1968 France ..68169192 US. Cl. ..260/92.8 R, 161/172, 161/177,

260/92.8 AC, 260/897 C, 260/899 Int. Cl. ..D01d 5/08 Field ofSearch..161/172, 175, 176, 177, 180, 161/181; 264/210; 260/876, 897, 899, 92.8A, 92.8

R, 92.8 AC

References Cited UNITED STATES PATENTS 2/1963 Shealy ..161/177 7/1963Merriam etal. ..161/171 3,164,948 1/1965 Stratford ..161/172 3,320,2055/1967 Imai et al... ....260/33.6

3,372,219 3/1968 Gord et al..... ....264/210 3,380,953 4/1968 Fukushima.....16l/17l 3,382,305 5/1968 Breen ....161/18l 3,444,269 5/1969 Beer..260/876 OTHER PUBLICATIONS L. Gord Polyvinyl Chloride Fibers fromMan-Made Fibers Science and Technology Vol. 3 Mark et al. (eds.) JohnWiley & Sons 1968 p. 333

Moncrieff Man Made Fibers (4th ed.) 1963 John Wiley & Sons New York pp.429- 430 Moncrieff Man Made Fibers Heywood Books: London (1966) pp. 64-65 Primary Examiner,Robert F. Burnett Assistant Examiner-Raymond O.Linker, Jr.

Attorney-Dale A. Bauer, John L. Seymour and Bauer and Seymour [57]ABSTRACT Vinyl chloride homoand co-polymers are made which have uniformcross section, homogeneous structure, great brilliance, and goodtransparency. They are far superior in these properties to any polyvinylchloride homoor co-polymers which were previously known. They may haveany desired shape in cross section, for instance those of a square or astar.

8 Claims, 4 Drawing Figures PATENTEBJUR 27 m2 SHEET 10F 2 INVENTORSCLAUDE LEDOUX Fig.2

BY ALBERT dc VRIES ATTORNEYS P'A'TENTEnJuw I972 3,673 167! sum 2 or 2INVENTORY) CLAUDE LE DOUX y ALBERT de VRIES ATTORNEYS POLYVINYL CHLORIDEFIBERS This application is a continuation-in-part of application Ser.No. 638,177, filed Apr. 24, 1967 now Pat. No. 3,548,049.

This invention relates to the manufacture of polyvinyl chloride inelongated shapes of uniform section, which had not heretofore beenaccomplished. Polyvinyl chloride fibers can be made by this process, areof substantial importance, and this invention will be related in itsapplication to their manufacture, it being understood that the processis equally applicable to the manufacture of other shapes the thicknessof which is minimum compared to length, for instance ribbons, pellicles,sheets.

Polyvinyl chloride has been made in shaped sizes of limited length bypressing in a mold or by extrusion, but polyvinyl chloride has not beenused to make highly flexible sizes of limitless length and minimumsection continuously. By limitless is meant to distinguish betweenobjects all the dimensions of which are fixed as made, compared to thoseof at least one indeterminate dimension.

Heretofore it has been possible to make polyvinyl chloride fiberscommercially only by dissolving the resin in a solvent, spinning thesolution, and evaporating the solvent, leaving a warped and unequalfiber as viewed against a black background. Such fibers are of unequalstrength, are unreproducible, contain solvent voids, and do not haveuniform luster when viewed by any kind of light. While the properties ofstrength and resistance to solvents of polyvinyl chloride theoreticallyindicate the desirability of polyvinyl chloride fibers, the difficultiesattending manufacture have prevented any substantial achievement of thatobjective. Proposals have been made to melt the fiber and extrude it buthave not been attended by success because of the sensitivity of thematerial to degradation by heat.

It is an object of the invention to make polyvinyl chloride fibers ofuniform section, uniform appearance and brilliant luster, transparentwhen desired, of any chosen cross section such as triangular, circular,elliptical, pellicular, solid or hollow, having the full strength of thematerial, resistant to solvents such as the chlorinated organicsolvents, and to make useful fibers not only of copolymers of vinylchloride but also of mixtures of these resins with'other resins whichare normally compatible, and surprisingly, with resins such as theethylenic and acrylate polymers which were formerly incompatible.

The objects are accomplished generally speaking by polyvinyl chloride inan elongated shape having an indeterminate dimension and a minimumsection, the section of which is substantially uniform, and by a methodof making a resinous composition from the class consisting of polyvinylchloride and its copolymers, and their mixtures with compatible andpreviously incompatible resins into elongated shapes of minimum sectionwhich comprises flowing a stream of molten polyvinyl chloride in theabsence of solvents and diluents toward shaping means, and homogenizingthe stream before its entering into the shaping means, heating thestream rapidly above the temperature of fusion of the crystallites ofthe resin, which is in the range of about 180 C. to 300 C., when usingcommercial types of polyvinyl chloride, thereby making it hot andplastic, shaping the hot, plastic resin in the shaping means drawing andcooling it, the heating, shaping, drawing and cooling of the homogeneousresin being limited to a time of the order of a few seconds to tens ofseconds.

The new fibers can be extruded, drawn, and made to rigid specificationsof uniformity not previously attainable, even to the manufacture ofrigorously exact transverse dimensions.

The above and further objects and novel features of the invention willmore fully appear from the following detailed description when the sameis read in connection with the drawings. It is to be expresslyunderstood, however, that the drawings are for purposes of illustrationonly and are not intended as a definition of the limits of theinvention.

In the drawings,

FIG. 1 is a view at 200 diameter enlargement through a phase contrastmicroscope of a fiber of polyvinyl chloride prepared from solution inaccordance with the prior art after such fiber has been spun andswollen;

FIG. 2 is a view through the same microscope at the same enlargement asFIG. 1 of a fiber of polyvinyl chloride made in accordance with theinvention after such fiber has undergone swelling;

FIG. 3 shows a polyvinyl chloride fiber made from solution in accordancewith the prior art and FIG. 4 shows a polyvinyl chloride fiber, at thesame enlargement as FIG. 3, which was made in accordance with thepresent invention.

In the new process the fibers are made from a melt of the resin withoutthe addition of solvent, being extruded from a spinnerette, for example,and drawn as they issue.

All types of polyvinyl chloride are useful in the process, e.g. thosepolymerized hot, those polymerized cold all its copolymers, e.g.polyvinyl chloride/vinylidene chloride, polyvinyl chloride/acrylonitrilesuper chlorinated polyvinyl chloride grafted polyvinyl chloride andthose in which the comonomer is ethylenic or acrylic. Particles ofdifferent polymers, e.g. polyvinyl chloride and polyvinylidene chloridecan be rapidly homogenized and heated and extruded together, producinguseful fibers of coordinate properties.

The process is of extreme rapidity, the completion of homogenization,extrusion drawing and the start of cooling being accomplished in lessthan a minute. To accomplish this the polyvinyl chloride flows in astream toward the spinnerette, the stream is homogenized just before thespinnerette by the most vigorous working, which impart a material risein temperature, is heated to melting temperature either just before thespinnerette, or in or before the die of the spinnerette itself, and iscooled by air or in a liquid. Before it is cooled it may be subjected todrawing. The whole operation will take less than a minute and in manycases only from a few seconds to a few tens of seconds.

The temperatures employed will vary according to the quality (e.g.viscosity and mol weight) of the resin. An exemplary polyvinyl chloridewas homogenized, melted, extruded, drawn, and cooled in 15 seconds at atemperature of 200 C. which was attained only for a few seconds.

A new machine has been described in French Pat. No. 1.461.398 and in itsfirst certificate of addition 90.529 and in U.S. Pat. No. 3,411,180which can be used in the present process.

The standard extrusion apparatus is useful, for instance spinnerettes,usually with the addition of means to heat the spinnerette and the zonesimmediately adjacent to it through which the homogenized resin flows, tothe temperature between 180 and 300 C. or above most useful with theparticular resin.

The fiber takes a shape closely corresponding to the shape of theextrusion orifice, e.g. circular, elliptical, lobed, triangular,cruciform. Such shapes could not previously be produced.

The invention not only provides for the formation of such articles frompolymers and copolymers but also from mixtures of different polymers andcopolymers, even those previously regarded as incompatible, and makesuseful articles from them, for instance from mixtures of vinyl resinswith olefinic and acrylic types.

The inventors have also found that the method of preparation of suchelongated bodies is practised in a facile manner if the gelification andmelting of the polymer are carried out at temperatures above 200 C. andwithin the range, for example, of from 220 to 290 C. and above, but bypreference from 230 C. to 260 C. In accordance with this method oneobtains thin fibers which have good drawability between and C.; thispermits fibers to be drawn down to as low as 2 deniers, such fibershaving a good strength and a good resistance to solvents. In such fibersthe phase constituted by a vinyl chloride homo-or co-polymer does notpresent any granular structure which is detectable by optical orelectron microscope.

In accordance with the invention the working temperature is chosen as afunction of the nature of the vinyl chloride polymers or copolymers, orof the compositions formed of mixtures of such polymers and copolymersand of polymer compositions of the olefin or acrylic ester type.

As an example, we have obtained fibers according to the invention from ahomopolymer of vinyl chloride, polymerized in mass and having an Afnorindex of viscosity of 80, stabilized with an organostannic compound, byextrusion by means of the apparatus described in French Pat. No.1,461,398 and in its certificate of addition No. 90.529. Such apparatuswas provided with an extrusion head provided with a die plate having 200circular cylindrical extrusion passages having a diameter of 1mm. Thetemperature measured with a thennocouple in the mass of molten polymerentering the extrusion head was 245 C., and the temperature of theextrusion head was maintained at 250 C. The polymer leaving the passagesin the die plate was drawn at a speed of 200 meters per minute, in azone subjacent the die plate wherein the air was maintained at atemperature of 170 C. for a distance of about 60 cm. by means of aheating sheath. The filaments thus obtained have an average size of 70deniers, and a stretchability at 100 C. of more than 1000 percent.

The fibers thus produced are perfectly homogeneous, and have no granularstructure. This is shown in FIG. 2, which is a view at 200 diameterenlargement through a phase contrast microscope of a fiber of polyvinylchloride made in accordance with the invention after such fiber hadundergone swelling by dichloroethane at ambient temperature for 30minutes. (Swelling in the classical manner by acetone is too small topermit a granular structure to appear if there were any).

FIG. 1 is a similar view at the same enlargement and in the samemicroscope as that employed in making FIG 2 of a fiber prepared from asolution of polyvinyl chloride in a mixture of equal parts by weight ofcarbon disulphide and acetone, such fiber being spun under dryconditions and swollen with acetone for 30 minutes at ambienttemperature. FIG. 1 clearly screw extruder having a screw with adiameter of 30 mm. and length/diameter ratio equal to 15. Thetemperature of the polymer measured in the extruder was 210 C., whilethe temperature of the die plate was held at 225 C. The drawing of thefilaments leaving the die plate was carried out under the sameconditions as those described above. The filaments obtained had anaverage size of 120 deniers and had a maximum stretchability at 100 C.of 500 percent, only one-half that of fibers made in accordance with theinvention. After such filaments have been swollen in dichloroethane, notrace of a granular structure can be detected in them by opticalmicroscope. Nevertheless, such filaments have qualities which areinferior to those of filaments made in accordance with the invention,and are no better than those of filaments obtained from solutions ofpolyvinyl chloride in accordance with prior art, particularly as totheir stretchability between 95 and 120 C. and the strength of theoriented filaments. Because of their low stretchability, filaments madeby a screw type extruder can not be made with sizes of less than aboutdeniers.

In Table 1 below there is set forth, by way of non-limiting examples, asummary of the comparative properties of three types of fibers made fromthe same polyvinyl chloride composition (l) fibers made from a solution,(2) fibers made by extrusion from a screw type extruder, and (3) fibersmade in accordance with the invention.

Table 1 shows that extrusion in a screw-extruder at 210 C. does notpermit the production of fibers having the same quality as the fibersmade according to our invention, in particular as to stretchability andultimate strength. An important characteristic of our invention is theextremely rapid melting and homogenizing procedure in order to obtain astream of molten polymer of relatively high temperature which is higherthan 200 C., the melting temperature of the crystallites in commercialpolyvinyl chloride.

Another characteristic of the invention is to maintain the polymerleaving the spinnerette at a sufiiciently high temperature which is atleast 170 C., during the drawing and before cooling, in order to obtaina high stretchability at 100 C.

TABLE l.--(EXAMPLES 1-6) Polyvinyl chloride pol merized in Filamentsobtained by dry spinning from a solution in a mixture of carbondisulphide-acetone Filaments obtained in accordance with the inventionby extruding in a plate extruder at 250 C.

Filaments obtained by extrusion in a single screw extruder at 210 C.

bulk index of viscosity-80 Ainor aver- After Alter After age molecularmass, in number, 37,500, N ondrawing Nondrawing Nondrawing in weight,70,000 oriented at 100 C. oriented at 100" C. oriented at 100 C.

Size (denier) -40 5-10 100-150 230- 40420 5-10 stretchability at 100 C.(times original length) 4-5 4-5 8-12 Strength (gJdenier) 0. 5 2. 0-2. 50. 5 2. 0-3. 0 O. 5 3. 5-4. 5 Elongation to rupture, percent 250 15-25250 l5-25 300-400 1525 Shrinkage in perchlorethylene at C. of drawnfilament fixed and retracted at 100" C.(percent). 20-30 5-7 2-4 showsthe granular structure of the fiber such granular structure lowers theresistance of the fiber to solvents, its stretchability, and itsstrength.

The remarkable difl'erences between the fibers of FIGS. 1 and 2 are alsoshown by measurement of their birefrin-gences. Fibers issuing fromsolution have a low birefringence A n 10', such birefringence rising tovalues on the order of 3 x 10 after the fibers have been drawn at 100 C.Polyvinyl chloride fibers made in accordance with the invention havevalues of birefringence which vary according to the conditions underwhich the fibers are drawn. Drawing of the fibers at 100 C. produces anappreciable molecular orientation in the fibers, as evidenced by valuesof A n of about 12 X 10'.

The inventors have also studied in a comparative manner filaments ofpolyvinyl chloride homopolymer, of the same composition as the two typesof fibers described above, obtained by extrusion in a molten state in aconventional single The following additional examples further illustratethe invention without detracting from the generality of what iselsewhere herein stated.

EXAMPLE 7 Granules of polyvinyl chloride of viscosity index stabilizedwith a standard stabilizer flow in a stream toward a small but powerfulhomogenizer in which they are homogenized and fluidified at 220 C. Thestream of molten polyvinyl chloride is immediately forced through aspinnerette having 350 holes of 1.5 mm. diameter, the spinnerette beingheld at 200 C. The passage through the extrusion apparatus took l0-15seconds and the fibers issuing from it were drawn at 50 m/min. A thermalconditioning zone was provided at the discharge part of the spinnerettewhich permitted the drawing to be completed before the fibers werecooled to set temperature. Ordinary drawing and winding apparatus wasused. Microscopic examination showed orientation, :1 diameter of 105microns, and a value of 122 deniers. The section was uniformly circular.The following characteristics were determined Heat loss 15 H at 60 C OStretch in boiling water 210 Shrinkage in boiling water after being set47 Shrinkage in oil at 120 C 16 Shrinkage in perchlorethylene at 60 C. 2Shrinkage in trichlorethylene at 50 C. 20

Strength of the undrawn fiber 0.77 g/denier Elongation at rupture 86Strength of the drawn and set fiber 1.82 g/denier Elongation of thedrawn and set fiber 35 Resistance of the set fiber released in boilingwater Elongation of the drawn set, and released fiber 1.07 g/de nierEXAMPLE 8 The apparatus of US. Pat. No. 3,41 1,180 was used, its speedaccelerated to 180 rpm. and it was supplied with polyvi nyl chloride ofindex of viscosity 80 which had been stabilized with a standard priorart stabilizer a fluid, homogeneous flow was obtained. The mean time ofthe flow in the extruder was 10-15 seconds. The flow was passed througha spinnerette heated to 220 C., drawing of the fibers at discharge wasat 250 m/min. The fibers were cooled and gathered by classic methods.The fibers were as above, oriented, brilliant, of circular crosssection, and uniform with a mean diameter of 26 microns and a titre of31 deniers. Their properties were Titre of undrawn fibers 31 deniersLoss on heating [5 H at 60 C 0 Stretch in boiling water 200 Shrinkage inboiling water after drawing and setting 40 Shrinkage in oil at 120 C.,of drawn and set fibers Shrinkage in trichlorethylene at 50 C Strength,of drawn and set fibers 2.2 g/denier Elongation, of drawn and set fibers24 Elongation after drawing, setting and shrinkage 100 EXAMPLE 9 Theconditions precedent were followed but a copolymer of vinyl chloride andpropylene (95/5) was used. The same brilliance and uniformity wasobserved. The properties were Titre 25 deniers Loss at 60 C after 15 H 0Stretch in boiling water 200 Shrinkage in boiling water of the fibersdrawn and fixed 45 Shrinkage in oil at 120 C of drawn Shrinkage intrichlorethylene Strength, of drawn and fixed fibers 1.9 g/denierElongation at rupture of drawn and Elongation at rupture of drawn,fixed,

and retracted fibers 1.1 g/denier Elongation at rupture of drawn, fixed,

and retracted fibers 130 EXAMPLE 10 The apparatus employed had a smallbut high speed mixer, a short tube leading from the mixer to thespinnerette which was heated to 200 C., the spinnerette being heated to220 C. A powder of mixed grains of polyvinyl chloride and polypropylene(90 to 10 percent) was supplied to the mixer and forced through thespinnerette. The speed of the extruded fibers measured after drawing was150 meters per minute. The spinnerette had 200 rectangular holes 3 mm onone side and 1.2 mm on the other. Total time of heating approached 25seconds. The temperature employed approached 220 C. The fibers were ofuniform section, had a titre of 35 deniers, had high and uniform luster,and retained their uniformity when drawn. Tests revealed the followingproperties:

Titre of undrawn fibers 35 deniers Weight loss at 60 C after 15 H 0Stretch in boiling water 220 Shrinkage of the drawn and set fibers inboiling water 32 7t Further shrinkage in oil at 120 C 20 Shrinkage intrichlorethylene at 50 C 32 7: Strength of the drawn and set fiber 2.75g/denier Elongation of the same at breaking 20 7r Strength of the drawn,set and shrunk fiber 1.8 g/denier Elongation of the same at rupture 70weight. This fiber has these properties Undrawn fiber 40 deniersLossat60Cin15H 0% Stretch in boiling water 200 Shrinkage of drawn andset fiber in boiling water 46 Shrinkage in oil at 120 C of the foregoing35 Shrinkage in trichlorethylene at 50 C 31 Strength of drawn and setfiber 1.7 g/denier Elongation at rupture 30 Strength of shrunk fiber0.99 g/denier Elongation of stretched set and shrunk fiber at rupture130 Example 12 Conditions were as in Ex. 11 but the spinnerette had 350circular holes 1.5 mm in diameter and the resin was a -10 mixture ofpolyvinyl chloride and polypropylene, not a copolymer. The spinnerettewas at 220 C. and drawing was at 250 m/min. The fibers tested thusUndrawn fibers 28 deniers Lossat60Cat 15H 0% Stretch in boiling water230 Shrinkage of the drawn and set fiber in boiling water 30 Shrinkagein oil at 120 C of the drawn,

set, and shrunken fiber 18 Shrinkage in 50 C trichlorethylene 30Strength of the drawn and set fiber 3.5 g/denier Elongation at ruptureof the drawn and set fiber 2O Strength of the drawn, set and shrunkenfiber Elongation of the foregoing at rupture EXAMPLE 1 3 Usingconditions similar either to Ex. 12 and a mixture of percent by weightpolyvinyl chloride and 5 percent 2.05 g/denier 70 polymethylmethacrylateproduced fibers having the qualities Undrawn 36 deniers Loss on heating0 Stretch in boiling water 200 Shrinkage after drawing and setting 45Shrinkage in hot oil after shrinkage in hot water 32 Shrinkage intrichlorethylene at 50 C 30 "7c Strength of the drawn and set fiber 2.5g/denier Elongation at rupture 24 Strength after setting and retraction1.15 g/denier Elongation of the foregoing at rupture 7c EXAMPLE 14Fabrics have been made on one hand with the novel fibers and on anotherhand with the fibers prepared according to a process of the prior art.In both cases pure polyvinyl chloride has been used in the fibers.

Fibers have been spun according to the novel process from polyvinylchloride of index of viscosity 80. Each fiber had a titre of 4. ldeniers after having been drawn at 950 m/min.

These fibers have been used to prepare yarns themselves woven to form afabric of the canvas type having the following characteristics 140'g/sq.m.

weight Warp: titre 200/64 deniers twisting 50 r/m Z number of threads28/cm FillingL: titre 200/64deniers twisting 50 r/m Z number of threads25/cm Strength measured according to the French Norm G 07001 warp 125 Kgfilling 107 Kg Sizes stability after 30 mn in perchlorethylene at 25Cshrinkagezwarp filling After 30 mn in trichlorethyle shrinkage2warpfilling less than 1 no at 25C A same fabric made with fibers of equalsizes but prepared according to the prior art, has the followingcharacteristics strengthzwarp filling 62,7 Kg Size stability after 30 mnin perchlorethylene at 25C shrinkagecwarp 6 filling 2 After 30 mn intrichloroethylene at 25C shrinkagezwarp 30 filling 22.5

guished from copolymers, homogeneity of composition may be lacking inappearance, two or more phases being visible under the microscope, buthomogeneity of properties is still present even in cases where theresins used were previously deemed too incompatible to be used together.In shape, total superiority is established because the resins can beextruded in the exact shape desired, which was totally impossible withsolvent systems of manufacture. Exact reproducibility of any fiber incomposition, appearance, and shape is achieved by this invention, a factwhich in itself vastly extends the use of polyvinyl chloride polymersand mixtures.

The new fibers may be flexible or stiff, thick or thin, solid ortubular, depending on the construction of the extrusion orifice. Theshapes may be pellicular, e.g. like ribbons, and of all other shapes ofequal or different transverse and vertical dimensions.

Modifiers may be included during the mixing, such as are normally usedwith such compositions, for instance, plasticizers and fillers.Inclusion of materials such as solvents capable of creating voids, is tobe avoided except when, for reasons pertaining to appearance, voids aredesired in the fiber, in which case loss of novel properties is to beexpected.

The novel fibers when extruded as pure resins are normally transparentand of high luster. Delustering agents heretofore satisfactory withpolyvinyl chloride may be included before or after extrusion. In caseswhere mixed resins produce a plurali ty of phases, novelty of attractiveappearance follows, sometimes accompanied by internal reflection andrefraction of light.

The physical and chemical characteristics of the novel products havingan indeterminate dimension and minimum section are superior to anythingpreviously known in materials of polyvinyl chloride base, comparedcomposition to composition.

The foregoing description is exemplary, not limitive.

What is claimed is:

l. Melt-spun fibers of a polyvinyl chloride resin, which are homogeneousin composition and appearance, transparent when viewed against a blackbackground under magnification,

' free from voids, and when viewed under a microscope appearstretchability of 1000 percent at C. and average titre of v 70 deniers.

4. Melt-spun fibers according to claim 1 which have been hot drawn to a5 to 10 deniers titre and which have a strength of from 3.5 to 4.5 gamsper denier.

5. Melt-spun fi rs according to claim 1 which have been drawn at 100 C.and exhibit a specific index of birefringence of 12 X 10'.

6. Melt-spun polyvinyl chloride fibers which are homogeneous incomposition and appearance, free from voids and from zones of strictionand strangulation, transparent against a black background and of greatbrilliance and which have a uniform section along the length when viewedunder a microscope, said fibers being drawable at 100C. fromsubstantially greater than 5 times to 8 to 12 times.

7. Drawn melt-spun polyvinyl chloride fibers which are homogeneous incomposition and appearance and which have been drawn to at least tentimes their extruded length, and which are transparent and which show nogranular structure under the electronic microscope and which have auniform cross-section along the length when viewed under the microscope.

8. Drawn melt-spun polyvinyl chloride fibers according to claim 7, whichhave been drawn at 100 C. exhibiting a molecular orientation asevidenced by a specific index of birefringence of 12 X 10 UNITED STATESPATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3,673, 167 Dated June27, 1972 ln n fl CLAUDE LEDOUX and ALBERT DE-VRIES It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

7 Column 1 on the TITLE PAGE, "[72]", line '1, change "Ledous" to LedouxColumn 7, line 25, change "trichlorethyle ne at 25C:" totrichlorethylene at 25C, line 39', change "trichloroethylene at 25C, totrichlorechylene at 25C.

Signed and sealed this 1st day of May 1973.

(SEAL) Attest:

EDWARD M. FLETCHER, ROBERT GOTTSCHALK httesting Officer Commissioner ofPatents

2. Melt-spun fibers according to claim 1, which have been drawn whilehot and have been set, and which have a shrinkage when heated inperchlorethylene at 60* C. of 2 to 4 percent.
 3. Melt-spun fibersaccording to claim 1 which have a stretchability of 1000 percent at 100*C. and average titre of 70 deniers.
 4. Melt-spun fibers according toclaim 1 which have been hot drawn to a 5 to 10 deniers titre and whichhave a strength of from 3.5 to 4.5 grams per denier.
 5. Melt-spun fibersaccording to claim 1 which have been drawn at 100* C. and exhibit aspecific index of birefringence of 12 X 10 3 .
 6. Melt-spun polyvinylchloride fibers which are homogeneous in composition and appearance,free from voids and from zones of striction and strangulation,transparent against a black background and of great brilliance and whichhave a uniform section along the length when viewed under a microscope,said fibers being drawable at 100* C. from substantially greater than 5times to 8 to 12 times.
 7. Drawn melt-spun polyvinyl chloride fiberswhich are homogeneous in composition and appearance and which have beendrawn to at least ten times their extruded length, and which aretransparent and which show no granular structure under the electronicmicroscope and which have a uniform cross-section along the length whenviewed under the microscope.
 8. Drawn melt-spun polyvinyl chloridefibers according to claim 7, which have been drawn at 100* C. exhibitinga molecular orientation as evidenced by a specific index ofbirefringence of 12 X 10 3 .